There have been known that silent discharge is caused by applying a high-voltage alternating current or a periodic pulse voltage on a dielectric body disposed between two electrodes fixed at both end portions to generate a plasma field, where an active species, a radical, and an ion are formed to promote reaction and decomposition of gas and that this can be used for removing harmful components contained in engine exhaust gas or exhaust gas from various kinds of incinerators.
For example, there is disclosed a plasma reactor which treats, e.g., NOx, carbon particulate, HC, and CO contained in engine exhaust gas or exhaust gas from various kinds of incinerators by passing the engine exhaust gas or exhaust gas from various kinds of incinerators through the plasma field (see, e.g., JP-A-2001-164925).